Psilocybe is a genus of gilled mushrooms growing worldwide. This genus is best known for its species with psychedelic properties. Psilocin and psilocybin are the psychedelic compounds responsible for the psychoactive effects of many species in the genus.

The word Psilocybe comes from the Greek words ψιλός + κύβη,[2] and literally means "bare headed", referring to the mushroom's detachable pellicle (loose skin over the cap). It is pronounced with the accent on the third syllable /sɪloʊˈsaɪbiː/.[3][4] The final e is not silent.

Psilocybefruit bodies are typically small, nondescript mushrooms with a typical "little brown mushroom" morphology. Macroscopically, they are characterized by their small to occasionally medium size, brown to yellow-brown coloration, with a typically hygrophanouscap, and a spore print-color that ranges from lilac-brown to dark purple-brown (though rusty-brown colored varieties are known in at least one species).[5] Hallucinogenic species typically have a blue-staining reaction when the fruit body is bruised. Microscopically, they are characterized by pileipellis with hyphae that run parallel to the pileus surface, forming a cutis, by their lack of chrysocystidia, and by spores that are smooth, ellipsoid to rhomboid to subhexagonal in shape, with a distinct apical germ pore. Ecologically, all species of Psilocybe are saprotrophs, growing on various kinds of decaying organic matter.[6][7]

A 2002 study of the molecular phylogeny of the agarics[8] indicated that the genus Psilocybe as then defined was polyphyletic, falling into two distinct clades that are not directly related to each other. The blue-staining hallucinogenic species constituted one clade and the non-bluing species the other. The previous type species (Psilocybe montana) of the genus was in the non-bluing clade, but in 2010 the type species was changed to Psilocybe semilanceata, a member of the bluing clade. A 2006 molecular phylogenetic study of the Agaricales by Matheny and colleagues, further demonstrated the separation of the bluing and non-bluing clades of Psilocybe in a larger, strongly supported phylogenetic tree of the Agaricales.[9]

Psilocybe had been placed taxonomically in the agaric family Strophariaceae based upon its spore and pileipellis morphology. The phylogenetic study by Matheny et al., placed the non-bluing Psilocybe and its close relatives in a basal position within the Strophariaceae, a sister taxon to a clade containing the other genera within that family. The bluing Psilocybe, however, form a clade that is sister to Galerina in the newly revised family, Hymenogastraceae that used to be restricted to secotioid, false-truffles.[9] The phylogenetic study by Moncalvo, et al. confirmed that the agaric genus Melanotus is simply a subgroup of the non-bluing Psilocybe, all of which are placed in Deconica, and also pointed to a close relationship between the latter genus and the genera Kuehneromyces and Phaeogalera.[8]

In 2007, a paper by Redhead et al. proposed conserving the genus Psilocybe with Psilocybe semilanceata as its type species.[10] The suggestion was accepted by unanimous vote of the Nomenclature Committee for Fungi of the International Botanical Congress in 2010, meaning that P. semilanceata (a member of the bluing clade) now serves as the type species of the genus.[11] Since P. semilanceata is now the type species of the genus, the bluing hallucinogenic clade remained in the genus Psilocybe (Hymenogastraceae) while the non-bluing clade were transferred to the genus Deconica (Strophariaceae).[12] However, it has been demonstrated that Psilocybe fuscofulva, a species that used to be known as Psilocybe atrobrunnea, belongs to the genus Psilocybe s.s. but does not contain psychotropic compounds.[13]

The psilocybin molecule is indirectly responsible for the hallucinogenic properties of the Psilocybe genus. This compound, as well as all other indole alkaloids, are derived from the amino acid tryptophan, being the only amino acid with the indole-amine ring. Tryptophan is converted to tryptamine by decarboxylation.[17] Two methylation steps occur producing DMT, another psychedelic compound.[17] Hydroxylation of this compound produces the more potent hallucinogen psilocin, followed by phosphorylation yielding psilocybin.[17] After ingestion of the psilocybin compound alkaline phosphatases present in the body's digestive system, kidneys, and possibly in the blood readily cleave the phosphoryl ester bond from psilocybin, yielding the hydroxyl compound, psilocin.[18] Psilocin is the chemical primarily responsible for the hallucinogenic effects of the Psilocybe genus.[18] The blue-staining species of Psilocybe are characterized by the presence of psilocin and psilocybin. This blue-staining reaction occurs after the fruit body has been injured, particularly near the base of the stalk.[19] This reaction is thought to be due to the oxidation of psilocybin after the outer surface of the fruit body has been breached.[20] The degree of bluing in a Psilocybe fruit body roughly correlates with the concentration of psilocin in the mushroom.[21] Psilocybin is chemically far more stable than psilocin, the latter compound being largely lost when the mushroom is heated or dried.[citation needed]

The chemical structure of serotonin, an innate indole alkaloid neurotransmitter that regulates our mood and therefore happiness, is nearly identical to that of psilocin. The latter differing mainly by the hydroxyl group moving one carbon and the addition of two methyl groups that make the molecule lipophilic (fat soluble), ergo capable of crossing the lipid membrane sheaths of the central nervous system.[22] After psilocybin has been ingested and dephosphorylated, to psilocin, the mechanism it uses in the brain has a direct agonist effect on the 5-HT serotonin receptors.[18] To explain this effect, the psilocin molecule essentially mimics the serotonin molecule, binding to the 5-HT receptors and initiating the same response as the serotonin. This effect explains the euphoria experienced by ingestion of this "agonist". Initially, hallucinogens were thought to blockade these serotonin neurotransmitters, but persistent research led to this agonist effect conclusion.[18]

Woolley and Campbell conducted research to determine whether the depletion of the hormone serotonin had a direct effect on mental disorders and that hallucinations might be due to an excess of serotonin.[23] Their results led them to study chemicals analogous to serotonin. They found that the psychoactive chemicals psilocybin and psilocin exhibited serotonin-like effects, however as dosage increased, these compounds acted as serotonin antagonists, psilocybin being comparable to the most potent antagonist yet discovered.[23] This is a plausible basis for the psychological effects of these hallucinogenic compounds.

Even though these chemicals are psychoactive and therefore the basidiomycete deemed toxic, there have been no reports of fatalities or induced internal organ damage directly associated with ingestion of these chemicals.[24] Misidentification of the fruit body could lead to ingestion of a lethal fungus.

The medicinal uses of the Psilocybe genus was recorded by Native Americans of Central America. Shamans, or curanderas would avidly ingest the "sacred mushrooms" for the extrasensory perceptual effects it gave them in order to better assess problems faced in their society.[25] The observed effects of the alkaloids found in these mushrooms has given rise to research into their possible uses for psychiatric medicine.[25] For details on contemporary research, see: Psilocybin: Medical research.

Hallucinogenic species of Psilocybe have a long history of use among the native peoples of Mesoamerica for religious communion, divination, and healing, from pre-Columbian times up to the present day. Hallucinogenic Psilocybe were known to the aboriginal Mexicans as teonanácatl (literally "divine mushroom")[26] and were reportedly served at the coronation of Moctezuma II in 1502. After the Spanish conquest of the Americas, the use of hallucinogenic plants and mushrooms, like other pre-Christian traditions, was forcibly suppressed and driven underground.[27]

By the 20th century, hallucinogenic mushroom use was thought by non-Native Americans to have disappeared entirely. However, in 1955, Valentina and R. Gordon Wasson became the first Westerners to actively participate in an indigenous mushroom ceremony. The Wassons did much to publicize their discovery, even publishing an article on their experiences in Life in 1957.[28] In 1956, Roger Heim identified the hallucinogenic mushroom that the Wassons had brought back from Mexico as Psilocybe and in 1958, Albert Hofmann first reported psilocin and psilocybin as the active compound in these mushrooms.[29] There is some skepticism in whether or not these "sacred mushrooms" were actually those of the Psilocybe genus. However, according to Heim's research in Mexico, he identified three species of Psilocybe that he believed were used in these Indian ceremonies. The species identified by Heim were; Psilocybe mexicana, P. caerulescen, and P. zapotecorum.[30][31][32] are a variety of Psilocybe mushrooms that make up the teonanácatl group of hallucinogenic mushrooms, including Psilocybe cubensis.[33] During Heim's field and culture work, he was under the guidance of a descendent of the Mazotecan ancestors (the natives which partook in experimenting with these hallucinogens), the head of the family, Isauro Nava Garcia.[34] He was an avid observer of the fungi in his environment while identifying specific characteristics about the fruit body of the Psilocybe genus his ancestors utilized, as well as knowing where they could be found.[34]

At present, hallucinogenic mushroom use has been reported among a number of groups spanning from central Mexico to Oaxaca, including groups of Nahua, Mixtecs, Mixe, Mazatecs, Zapotecs, and others.[35]

The popularization of entheogens by Wasson, Timothy Leary, and others has led to an explosion in the use of hallucinogenic Psilocybe throughout the world. By the early 1970s, a number of psychoactive Psilocybe species were described from temperate North America, Europe, and Asia and were widely collected. Books describing methods of cultivating Psilocybe cubensis in large quantities were also published. The relatively easy availability of hallucinogenic Psilocybe from wild and cultivated sources has made it among the most widely used of the hallucinogenic drugs.

The purified chemicals psilocybin and psilocin are listed as Schedule I drugs under the United Nations 1971 Convention on Psychotropic Substances.[36] However, the UN drug treaties do not apply to cultivation, preparation, or international transport of psilocybin mushrooms.

Internationally, the two chemicals are generally considered controlled substances. However, there is much ambiguity about what is considered a "container" of these compounds in several countries (e.g. Brazil), the chemicals themselves are listed as controlled substances, but the mushrooms that contain the chemicals are not, therefore deemed legal.[37] In the United States, possession of Psilocybe mushroom fruiting bodies is illegal in every state except for Florida. This is because the Supreme Court of Florida does not believe that these mushrooms could "reasonably be found to be containers of the schedule I substance, psilocybin".[38]

In the United States there is no federal law mentioning the possession of Psilocybe spores, this is because only the psilocybin and psilocin compounds are considered Schedule I drugs and there is no presence of these compounds in the spores themselves, only in the fruiting body of the cultivated spores. However, there are several US states that have actually prohibited possession of these spores because they can be cultivated to produce these hallucinogenic, Schedule I drugs. These states includes California, Georgia,[39] and Idaho.[37][40]

However, possession of the spores by a qualified mycologist in California is legal if being put to use for research purposes, which must be approved by Research Advisory Panel.[41] If not authorized by law, possession of spores or cultivation of fruiting bodies of the Psilocybe genus is punishable to not more than one year in county jail or state prison.[41]

Psilocybin mushrooms as well as other "soft drugs" which are stronger than cannabis but not synthetic, are legally available through smart shops in The Netherlands. Only the truffle form of magic mushrooms (such as Psilocybe tampanensis) are currently legal, but these still contain the active ingredients and produce similar effect as the caps and stalks.[42]

Psilocybe cubensis (Stropharia cubensis); the most commonly cultivated and consumed Psilocybe,[43] due to ease of cultivation and large size of fruit bodies; also commonly collected throughout the tropics and subtropics, nicknamed the commercial psilocybe.

^Stamets, 1996, p. 53. "The bluing reaction is obvious in the more potent species, especially those high in psilocin. In general, the less psilocin there is in a species, the more subtle the bluing reaction."

Guzmán G. (1983). The genus Psilocybe: A Systematic Revision of the Known Species Including the History, Distribution and Chemistry of the Hallucinogenic Species. Nova Hedwigia Beihefte. 74. Berlin, Germany: J. Cramer. ISBN3-7682-5474-7.